The primary aim of this research is to obtain an understanding of the chemical-physical basis for glucagon structure-biological activity relationships with the goal of developing glucagon analogues and derivatives which can act as specific inhibitors (antagonists) of glucagon action. We will then utilize these glucagon antagonists to obtain a deeper understanding of the role of glucagon in the normal state and in diabetes mellitus. An ultimate goal of this research is the design, synthesis, and development of an orally active glucagon antagonist for use in the treatment of diabetes mellitus. Recently we have developed a number of glucagon inhibitors (antagonists), and have demonstrated that the most active one can dramatically lower blood glucose levels in diabetic animals. We propose to follow up on the structural, synthetic, chemical, and biological insights we have gained from these studies in several ways: 1) we will further examine the in vivo and in vitro biological activities of our glucagon antagonists; 2) develop further synthetic and semisynthetic methods to obtain more potent, longer acting glucagon antagonist analogues (including fragment analogues); 3) carefully examine conformational and dynamic properties of the glucagon agonist and antagonist analogues and structure-biological activity relationships of these analogues in several assay systems, and then utilize this data to design (and synthesize) more potent antagonists; 4) develop better analytical and preparative purification methods, especially high pressure liquid chromatography, for glucagon and its analogues and derivatives so that the purest possible synthetic and semisynthetic analogues can be obtained; 5) examine the properties of glucagon receptors including the effects of ions and co-factors on glucagon agonist and antagonist binding; and 6) continue collaborations on the potential use of glucagon antagonists for the treatment of diabetes.